Coating particles of active materials (e.g. lithium titanate (LTO), TiO2 or others) with carbon is one way of avoiding contact between the active material and electrolyte, thereby preventing degradation of the electrolyte and the formation of gas inside the cell. The carbon coating creates a physical barrier and also enhances the material's electronic conductivity. Carbon can thus be applied on any active materials where improved stability and/or electronic conductivity is required or desirable (see He, Y.-B. et al., J. Power Sources, 2012, 202, 253-261, incorporated by reference in its entirety for all purposes).
One of the most common ways of applying a carbon coating on inorganic materials (LFP, LTO, TiO2 etc.) for lithium batteries includes the use of a sugar or sugar derivative as a carbon source. The sugar is mixed with the active material, for instance in a solvent, and carbonized at high temperature (see (a) Zaghib, K. et al., J. Power Sources, 2010, 195 (24), 8280-8288; (b) Zhu, G.-N. et al., J. Electrochem. Soc., 2011, 158 (2), A102-A109, both incorporated by reference in their entirety for all purposes). This process generally does not allow for the formation of a thin coating on primary particles and/or inside the pores of the particles. Additionally, the electronic conductivity of commercial carbon coated material produced by this method is limited to about 10−6 S/cm. It is thus not trivial to achieve the formation of a nano-layer of carbon on active particles using the sugar carbonization method.